Optical fiber ribbon with improved stripability

ABSTRACT

An optical fiber ribbon includes a plurality of optical fibers encapsulated within a matrix material, where the optical fiber coating(s) and the matrix material(s), and optionally any ink layers thereon, are characterized by compatible chemical and/or physical properties, whereby the fiber coating and matrix and any ink layers therebetween can be reliably stripped from the optical fibers to afford a suitable strip cleanliness. Novel ink formulations that can be used in the making of such fiber optic ribbons, methods of making such ribbons, and their use are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/291,565, filed on Nov. 30, 2005 now U.S. Pat. No. 7,257,299, thecontent of which is relied upon and incorporated herein by reference inits entirety, and the benefit of priority under 35 U.S.C. §120 is herebyclaimed.

FIELD OF THE INVENTION

The present invention relates generally to optical fiber and opticalfiber ribbons, and more particularly to coatings for optical fiber andto curable compositions for use in coating optical fiber.

BACKGROUND OF THE INVENTION

Optical fibers are often bundled together in parallel fashion to form aproduct known as an optical fiber ribbon. The ribbon includes opticalfibers that have been encased in a polymeric matrix material to securethe fibers in the parallel arrangement. The matrix portion of the ribboncan include one or more layers of the polymeric matrix material, andeach optical fiber typically contains a dual layer coating system thatincludes a soft, inner polymer coating and a hard, protective outerpolymer coating. Prior to forming the ribbon, the optical fibers mayalso be coated with a thin colored layer of marking ink (i.e., in apolymer base) for purposes of fiber identification within the ribbon.

The most basic function of the ink is to provide a means for identifyingindividual fibers in both ribbon and loose tube cables duringinstallation. Photoinitiators are used to initiate the polymerizationprocess when the inks are exposed to UV light during the inking process.The pigments also absorb light so obtaining a fast cure speed is achallenge. Fast cure speed is desired as the ink should be well curedprior to putting the fibers in a ribbon or cable. If the ink isunder-cured this can cause problems including, but not limited to,increased surface friction, poor ribbon peel performance (where thematrix material forms a very high bond with the ink due to residualacrylate groups on the ink surface), and the propensity for the inklayer to come off of the fiber during ribbon handling or stripping. Afast cure speed is also desirable to ensure robust process performance.For example, if the lamp intensity becomes low or the quartz tube in thelamp assembly becomes dirty, less UV light will be available to cure theinks and the result will be a low degree of cure on the inked fiber.Inks with low cure speeds are also disadvantaged from the standpointthat inking line speeds cannot be increased to facilitate higher output.Therefore, there is a need for radiation curable marking inks that havesufficient cure speed to overcome the above described challenges.

During use, the ribbon unit must be stripped prior to splicingoperations in the field. Stripping is usually performed using thermalstrippers (e.g., Sumitomo ribbon stripper model JR-4A) at operatingtemperatures in the range of 70-100° C. For successful splicing, it isimperative that the polymer layers (inner and outer coatings, inkcoating, matrix material) be removed from the ribbon cleanly and in anintact unit, i.e., leaving little debris on the stripped glass fiber.With an undesirable amount of debris, it is necessary to remove thedebris, for example, by wiping the stripped fibers with analcohol-moistened cloth. Unfortunately, with more debris, it is oftennecessary to wipe the fibers more than once. Correcting the problem ofexcessive debris therefore requires additional labor, time, and cost.Additionally, the act of repeated wiping may have the undesiredconsequence of weakening the glass fiber within the splice junction. Forthese reasons, wiping of the stripped glass fibers should be kept to aminimum.

Strip cleanliness is conventionally measured on a five-point scale, witha score of five being unclean and a score of one being clean. While thestrip cleanliness will vary according to the needs, it is generallydesirable for a stripped ribbon to possess optic fibers rated at acleanliness of three or lower, more preferably two or lower. Tube-off isalso measured on a five-point scale and is used as a means to assess theintegrity of the polymers layers that are removed from the ribbon. Ascore of one means the polymer layers can be removed in an intact unit.A score of five means that there is total disintegration of the polymerlayers and that they are not removed in an intact unit. As with thestrip cleanliness, it is generally desirable for the optical fiberribbon to possess a tube-off rating of three or lower, more preferablytwo or lower as this results in a reduced need to clean the strip tool,thus reducing splicing time.

Previous attempts to solve this problem have focused exclusively on theproperties of the matrix material. One such approach is disclosed inU.S. Pat. No. 6,501,890 to Wilson et al., which suggests using a matrixmaterial that exhibits a maximum tensile strength at 100° C. of at leastabout 1000 psi and an elongation at break at 100° C. of at least about15 percent. Focusing on the properties of the matrix material, alone,ignores any interactions between the other polymeric materials thatsurround the glass fibers.

The present invention is directed to overcoming the above-noteddeficiencies in the art, and achieving an optical fiber ribbon thatpossesses improved strip cleanliness and tube-off over a range oftemperatures and strip conditions.

SUMMARY OF THE INVENTION

A first aspect of the present invention relates to an optical fiberribbon that includes a plurality of optical fibers encapsulated within amatrix material, where the optical fiber coating(s) and the matrixmaterial(s), and optionally any ink layers thereon, are characterized bycompatible chemical and/or physical properties, whereby the fibercoating and matrix and any ink layers therebetween can be reliablystripped from the optical fibers to afford a suitable strip cleanliness.

According to one embodiment, the coating, matrix, and ink layer (ifpresent) are each characterized by a glass transition temperature(T_(g)) and a fracture toughness (K_(1C)) value, and one or more of thefollowing conditions are satisfied:

(i) the difference between the highest and lowest of the respectiveT_(g) values is less than about 15° C.,

(ii) the respective T_(g) values are at least about 60° C.,

(iii) the respective K_(1C) values are at least about 0.8 MPa·m^(1/2),or

(iv) any two or more of (i), (ii), and (iii) are satisfied.

According to another embodiment, the coating, matrix, and ink layer (ifpresent) are formed of a similar curable base formulation. That is,prior to forming the coating, matrix, or ink layer, the base formulationof oligomers and monomers is substantially similar and, consequently,compatible for use together.

A second aspect of the present invention relates to a telecommunicationsystem that includes one or more optical fiber ribbons according to thefirst aspect of the present invention.

A third aspect of the present invention relates to an ink formulationthat includes a pigment binder phase, a pigment or dye, and a phosphineoxide photoinitiator, wherein the ink formulation is characterized by acure speed of at least about 80 percent acrylate conversion/second forthe colors blue, green, yellow, black and brown, about 110 percentacrylate conversion/second for the color red, about 130 percent acrylateconversion/second for the colors orange and aqua, about 140 percentacrylate conversion/second for the colors white, violet and rose, andabout 150 percent acrylate conversion/second for the color slate.

A fourth aspect of the present invention relates to a method of makingan optical fiber ribbon that includes the steps of: providing aplurality of optical fibers, each having a coating; optionally applyingan ink composition at least partially to one or more of the plurality ofoptical fibers; encapsulating the plurality of optical fibers in amatrix composition; and curing the matrix composition (and optionallythe ink composition) to form an optical fiber ribbon according to thepresent invention.

By providing an optical fiber ribbon having polymeric coating, ink, andmatrix materials that have compatible thermal-mechanical properties, thevarious coatings are better able to cooperate during the strippingprocess (that is, they behave similarly under the stripping conditions)to afford a consistent and suitable degree of strip cleanliness duringstripping under both optimal and adverse conditions. Consequently, theuse of such ribbons will afford significant savings during theinstallation of optical fiber ribbons in telecommunication transmissionsystems.

Additional features and advantages of the invention will be set forth inthe detailed description which follows, and in part will be readilyapparent to those skilled in the art from the description or recognizedby practicing the invention as described in the written description andclaims hereof, as well as in the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary of theinvention, and are intended to provide an overview or framework forunderstanding the nature and character of the invention as it isclaimed.

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings are not necessarily to scale,and sizes of various elements may be distorted for clarity. The drawingsillustrate one or more embodiment(s) of the invention, and together withthe description serve to explain the principles and operation of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an optical fiber ribbon according toan embodiment of the present invention.

FIG. 2 is a cross-sectional of an optical fiber that includes adual-coating system and an optional marking ink layer thereon.

FIG. 3 is a schematic view of a film sample used in the measurement offracture toughness.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to optical fiber ribbons and methods ofmaking such ribbons, whereby the ribbons are capable of exhibitingimproved fiber stripability under both normal and adverse strippingconditions.

Referring to both FIGS. 1 and 2, optical fiber ribbons 10 of the presentinvention include a plurality of substantially aligned optical fibers 20that are encapsulated within a matrix 30. Each of the optical fibers 20includes a glass fiber 22 (i.e., core and one or more cladding layers),and at least one but preferably two or more coatings 24, 26. Typicaloptical fibers utilize a dual coating system that includes a soft,pliable inner or primary coating 24 and a hard, protective outer orsecondary coating 26. The matrix can be either a single layer matrix ora dual layer matrix (formed of inner and outer matrix materials). Inaddition to the coatings on the optical fiber itself and the matrix, anoptional ink layer 28 can be applied to one or more of plurality ofoptical fibers to allow for identification of individual optical fibers.

The primary coating 24 is formed from a soft, crosslinked polymermaterial having a low Young's modulus (e.g., less than about 5 MPa at25° C.) and a low glass transition temperature (T_(g)) (e.g., less thanabout −10° C.). The primary coating desirably has a higher refractiveindex than the cladding of the optical fiber in order to allow it tostrip errant optical signals away from the optical fiber cladding. Theprimary coating should maintain adequate adhesion to the glass fiberduring thermal and hydrolytic aging, yet be strippable therefrom forsplicing purposes. The primary coating typically has a thickness in therange of 25-40 μm (e.g., about 32.5 μm). Primary coatings are typicallyapplied to the glass fiber as a liquid and cured, as will be describedin more detail hereinbelow. Conventional curable compositions used toform primary coatings are formulated using an oligomer (e.g., apolyether urethane acrylate), one or more monomer diluents (e.g.,ether-containing acrylates), a photoinitiator, and other desirableadditives (e.g., antioxidant). Primary coatings for optical fibers havebeen well-described in the past, and are familiar to the skilledartisan. Desirable primary coatings are disclosed in U.S. Pat. No.6,326,416 to Chien et al., U.S. Pat. No. 6,531,522 to Winningham, U.S.Pat. No. 6,539,152 to Fewkes et al., U.S. Pat. No. 6,849,333 to Schisselet al., U.S. Pat. No. 6,563,996 to Winningham, and U.S. Pat. No.6,869,981 to Fewkes et al.; and U.S. Patent Application Publ. No.20030123839 to Chou et al., each of which is incorporated herein byreference in its entirety.

As noted above, the primary coating is typically surrounded by asecondary coating 26. Although the secondary coating is usually applieddirectly to the primary coating, the skilled artisan will recognize thatthere may be one or more intermediate coating layers deposited betweenthe primary coating and the secondary coating. The secondary coating isformed from a cured polymeric material, and typically has a thickness inthe range of 20-35 μm (e.g., about 27.5 μm). The secondary coatingdesirably has sufficient stiffness to protect the optical fiber; isflexible enough to be handled, bent, or spooled; has low tackiness toenable handling and prevent adjacent convolutions on a spool fromsticking to one another; is resistant to water and chemicals such asoptical fiber cable filling compound; and has adequate adhesion to thecoating to which it is applied (e.g., the primary coating).

The cured polymeric materials used in the secondary coatings of theoptical fibers may be the cured product of a curable compositionincluding an oligomer and at least one monomer. As is conventional, thecurable compositions used in forming the secondary coatings may alsoinclude photoinitiators, antioxidants, and other additives familiar tothe skilled artisan. In desirable embodiments of the invention, theoligomer and monomers of the curable composition are ethylenicallyunsaturated and contain (meth)acrylate functional groups to facilitatecuring. The oligomer may be, for example, a urethane (meth)acrylateoligomer. However, as the skilled artisan will recognize, oligomers andmonomers adapted for other curing chemistries, such as epoxy, vinylether, and thiol-ene, may be used in accordance with the presentinvention.

Suitable functional groups for ethylenically unsaturated monomers usedin accordance with the present invention include, without limitation,acrylates, methacrylates, acrylamides, N-vinyl amides, styrenes, vinylethers, vinyl esters, acid esters, and combinations thereof (i.e., forpolyfunctional monomers).

Exemplary polyfunctional ethylenically unsaturated monomers include,without limitation, alkoxylated bisphenol A diacrylates such asethoxylated bisphenol A diacrylate with ethoxylation being 2 or greater,preferably ranging from 2 to about 30 (e.g., SR349 and SR601 availablefrom Sartomer Company, Inc. (West Chester, Pa.) and Photomer 4025 andPhotomer 4028, available from Cognis Corp. (Ambler, Pa.)), andpropoxylated bisphenol A diacrylate with propoxylation being 2 orgreater, preferably ranging from 2 to about 30; methylolpropanepolyacrylates with and without alkoxylation such as ethoxylatedtrimethylolpropane triacrylate with ethoxylation being 3 or greater,preferably ranging from 3 to about 30 (e.g., Photomer 4149 (CognisCorp.) and SR499 (Sartomer Company, Inc.)), propoxylatedtrimethylolpropane triacrylate with propoxylation being 3 or greater,preferably ranging from 3 to 30 (e.g., Photomer 4072 (Cognis Corp.) andSR492 (Sartomer)), and ditrimethylolpropane tetraacrylate (e.g.,Photomer 4355 (Cognis Corp.)); alkoxylated glyceryl triacrylates such aspropoxylated glyceryl triacrylate with propoxylation being 3 or greater(e.g., Photomer 4096 (Cognis Corp.) and SR9020 (Sartomer)); erythritolpolyacrylates with and without alkoxylation, such as pentaerythritoltetraacrylate (e.g., SR295 (Sartomer)) ethoxylated pentaerythritoltetraacrylate (e.g., SR494 (Sartomer)), and dipentaerythritolpentaacrylate (e.g., Photomer 4399 (Cognis Corp.) and SR399 (Sartomer));isocyanurate polyacrylates formed by reacting an appropriate functionalisocyanurate with an acrylic acid or acryloyl chloride, such astris-(2-hydroxyethyl)isocyanurate triacrylate (e.g., SR368 (Sartomer))and tris-(2-hydroxyethyl)isocyanurate diacrylate; alcohol polyacrylateswith and without alkoxylation such as tricyclodecane dimethanoldiacrylate (e.g., CD406 (Sartomer)) and ethoxylated polyethylene glycoldiacrylate with ethoxylation being 2 or greater, preferably ranging fromabout 2 to 30; epoxy acrylates formed by adding acrylate to bisphenol Adiglycidylether (4 or more oxyethylene groups) and the like (e.g.,Photomer 3016 (Cognis Corp.)); and single and multi-ring cyclic aromaticor non-aromatic polyacrylates such as dicyclopentadiene diacrylate anddicyclopentane diacrylate.

Exemplary monofunctional ethylenically unsaturated monomers include,without limitation, hydroxyalkyl acrylates such as2-hydroxyethyl-acrylate, 2-hydroxypropyl-acrylate and2-hydroxybutyl-acrylate (Aldrich); long- and short-chain alkyl acrylatessuch as methyl acrylate (Aldrich), ethyl acrylate (Aldrich), propylacrylate (Aldrich), isopropyl acrylate, butyl acrylate (Aldrich), amylacrylate, isobutyl acrylate (Aldrich), t-butyl acrylate (Aldrich),pentyl acrylate, isoamyl acrylate, hexyl acrylate (Aldrich), heptylacrylate, octyl acrylate, isooctyl acrylate (e.g. SR 440 Sartomer),2-ethylhexyl acrylate (Aldrich), nonyl acrylate, decyl acrylate,isodecyl acrylate (e.g. SR 395 Sartomer), undecyl acrylate, dodecylacrylate, lauryl acrylate (e.g. SR 335 Sartomer), octadecyl acrylate(Aldrich), and stearyl acrylate (e.g. SR257 Sartomer); amino alkylacrylates such as dimethylaminoethyl acrylate (Aldrich), diethylaminoethyl acrylate (Aldrich), and 7-amino-3,7-dimethyloctyl acrylate;alkoxyalkyl acrylates such as butoxylethyl acrylate (Aldrich),phenoxyethyl acrylate (e.g., SR339 Sartomer)), and ethoxyethoxyethylacrylate (SR 256 Sartomer); single and multi-ring cyclic aromatic ornon-aromatic acrylates such as cyclohexyl acrylate, benzyl acrylate,dicyclopentadiene acrylate, dicyclopentanyl acrylate, tricyclodecanylacrylate, bornyl acrylate, isobornyl acrylate (e.g., SR506 (Sartomer)),tetrahydrofurfuryl acrylate (e.g., SR285 (Sartomer)), caprolactoneacrylate (e.g., SR495 (Sartomer)), and acryloylmorpholine alcohol-basedacrylates such as polyethylene glycol monoacrylate (Aldrich),polypropylene glycol monoacrylate (Aldrich), methoxyethylene glycolacrylate, methoxypolypropylene glycol acrylate, methoxypolyethyleneglycol acrylate, ethoxydiethylene glycol acrylate, and variousalkoxylated alkylphenol acrylates such as ethoxylated (4) nonylphenolacrylate (e.g., Photomer 4003 (Henkel)); acrylamides such as diacetoneacrylamide (Aldrich), isobutoxymethyl acrylamide (Aldrich),N,N′-dimethyl-aminopropyl acrylamide, N,N-dimethyl acrylamide (Aldrich),N,N-diethyl acrylamide (Aldrich), and t-octyl acrylamide; vinyliccompounds such as N-vinylpyrrolidone (ISP Corporation) andN-vinylcaprolactam (ISP Corporation); and acid esters such as maleicacid ester and fumaric acid ester.

Most suitable monomers are either commercially available or readilysynthesized using reaction schemes known in the art. For example, mostof the above-listed monofunctional monomers can be synthesized byreacting an appropriate alcohol or amine with an acrylic acid oracryloyl chloride.

The oligomeric component can include a single type of oligomer or it canbe a combination of two or more oligomers. When employed, if at all, theoligomeric component introduced into the compositions of the presentinvention preferably comprises ethylenically unsaturated oligomers.While the oligomeric component can be present in an amount of 15 weightpercent or less, it is preferably present in an amount of about 13weight percent or less, more preferably about 10 weight percent or less,even more preferably less than about 10 percent, and most preferablyabout 9 percent of less. While maintaining suitable physicalcharacteristics of the composition and its resulting cured material, itis more cost-effective and, therefore, desirable to prepare compositionscontaining preferably less than about 5 weight percent or substantiallydevoid of the oligomeric component.

When employed, suitable oligomers can be either monofunctional oligomersor polyfunctional oligomers, although polyfunctional oligomers arepreferred. The oligomeric component can also be a combination of amonofunctional oligomer and a polyfunctional oligomer.

Di-functional oligomers preferably have a structure according to formula(I) below:F—R₁-[Diisocyanate-R₂-Diisocyanate]_(m)-R₁—F  (I)wherein,

-   -   F is independently a reactive functional group such as acrylate,        methacrylate, acrylamide, N-vinyl amide, styrene, vinyl ether,        vinyl ester, or other functional group known in the art;    -   R₁ includes, independently, —C₂₋₂₀—, —C₂₋₄—O)_(n)—,        —C₂₋₂₀—(C₂₋₄—O)_(n)—, —C₂₋₂₀—(CO—C₂₋₅—O)_(n)—, or        —C₂₋₂₀—(CO—C₂₋₅—NH)_(n) where n is a whole number from 1 to 30,        preferably 1 to 10;    -   R₂ is polyether, polyester, polycarbonate, polyamide,        polyurethane, polyurea, or combinations thereof; and    -   m is a whole number from 1 to 10, preferably 1 to 5.        In the structure of formula (I), the diisocyanate group is the        reaction product formed following bonding of a diisocyanate to        R₂ and/or R₁. The term “independently” is used herein to        indicate that each F group may differ from another F group and        the same is true for each R group.

Other polyfunctional oligomers preferably have a structure according toformulae (II), (III), or (IV) as set forth below:multiisocyanate-(R₂—R₁—F₂)_(x)  (II)(polyol-[(diisocyanate-R₂-diisocyanate)_(m)-R₁—F₂]_(x)  (III)or multiisocyanate-(R₁—F₂)_(x)  (IV)wherein,

-   -   F₂ independently represents from 1 to 3 functional groups such        as acrylate, methacrylate, acrylamide, N-vinyl amide, styrene,        vinyl ether, vinyl ester, or other functional groups known in        the art;    -   R₁ can include —C₂₋₂₀, —(C₂₋₄—O)_(n)—, —C₂₋₂₀—(C₂₋₄—O)_(n)—,        —C₂₋₂₀—(CO—C₂₋₅—O)_(n)—, or —C₂₋₂₀—(CO—C₂₋₅—NH)_(n) where n is a        whole number from 1 to 30, preferably 1 to 10;    -   R₂ can be polyether, polyester, polycarbonate, polyamide,        polyurethane, polyurea or combinations thereof;    -   x is a whole number from 1 to 10, preferably 2 to 5; and    -   m is a whole number from 1 to 10, preferably 1 to 5.        In the structure of formula II, the multiisocyanate group is the        reaction product formed following bonding of a multiisocyanate        to R₂. Similarly, the diisocyanate group in the structure of        formula III is the reaction product formed following bonding of        a diisocyanate to R₂ and/or R₁.

Urethane oligomers are conventionally provided by reacting an aliphaticdiisocyanate with a hydric polyether or polyester, most typically apolyoxyalkylene glycol such as a polyethylene glycol. Such oligomerstypically have between about four to about ten urethane groups and maybe of high molecular weight, e.g., 2000-8000. However, lower molecularweight oligomers, having molecular weights in the 500-2000 range, mayalso be used. U.S. Pat. No. 4,608,409 to Coady et al. and U.S. Pat. No.4,609,718 to Bishop et al., each of which is hereby incorporated byreference in its entirety, describe such syntheses in detail.

When it is desirable to employ moisture-resistant oligomers, they may besynthesized in an analogous manner, except that the polar polyether orpolyester glycols are avoided in favor of predominantly saturated andpredominantly nonpolar aliphatic diols. These diols include, forexample, alkane or alkylene diols of from about 2-250 carbon atoms and,preferably, are substantially free of ether or ester groups.

As is well known, polyurea components may be incorporated in oligomersprepared by these methods, simply by substituting diamines or polyaminesfor diols or polyols in the course of synthesis. The presence of minorproportions of polyurea components in the coating systems is notconsidered detrimental to coating performance, provided only that thediamines or polyamines employed in the synthesis are sufficientlynon-polar and saturated so as to avoid compromising the moistureresistance of the system.

The total oligomer content of the secondary coating composition ispreferably less than about 25%, and the total monomer content is greaterthan about 65%. In especially desirable embodiments, the total oligomercontent is less than about 15% and the total monomer content is greaterthan about 75%. Use of relatively low amounts of oligomer allows theskilled artisan to easily formulate curable compositions having adesirable viscosity. As the oligomer is typically a more expensivecomponent of the composition, minimization of the amount of oligomeralso allows the skilled artisan to reduce the cost of the curablecomposition, as well as the cost of articles, such as optical fibers,coated therewith. Secondary coating compositions having low oligomercontent are described in more detail in U.S. Pat. No. 6,775,451 toBotelho et al., which is hereby incorporated by reference in itsentirety. The oligomer is desirably present in the curable compositionat a concentration of at least about 1 wt %.

The curable compositions, both primary and secondary compositions, mayalso include a polymerization initiator. Any suitable photoinitiator canbe introduced into compositions of the present invention. The initiatoris desirably present in an amount effective to initiate polymerizationof the curable composition. Polymerization initiators suitable for usein the curable compositions include thermal initiators, chemicalinitiators, electron beam initiators, microwave initiators, actinicradiation initiators, and photoinitiators. Preferred curablecompositions of the present invention are adapted to be cured by actinicradiation, and include one or more photoinitiators. For most(meth)acrylate-based curable compositions, conventional photoinitiators,such as ketonic and/or phosphine-oxide based initiators, may be used.Generally, the total photoinitiator content of the curable compositionis between about 0.1 and about 10.0 weight percent. More desirably, thetotal photoinitiator content of the curable composition is between about1.0 and about 7.5 weight percent.

Suitable photoinitiators include, without limitation,1-hydroxycyclohexylphenyl ketone (e.g., Irgacure 184 (Ciba SpecialtyChemical, Tarrytown, N.Y.)), (2,6-1dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide (e.g., incommercial blends Irgacure 1800, 1850, and 1700 (Ciba)),2,2-dimethoxy-2-phenyl acetophenone (e.g., Irgacure 651 (Ciba)),bis(2,4,6 trimethylbenzoyl)phenyl phosphine oxide (e.g., Irgacure 819(Ciba)), (2,4,6-trimethylbenzoyl)diphenyl phosphine oxide (e.g., incommercial blend Darocur 4265 (Ciba)),2-hydroxy-2-methyl-1-phenylpropane-1-one (e.g., in commercial blendDarocur 4265 (Ciba)), and combinations thereof. Other photoinitiatorsare continually being developed and used in coating compositions onglass fibers. Any suitable photoinitiator can be introduced intocompositions of the present invention.

In addition to the above-described components, the secondary coatingcompositions can optionally include an additive or a combination ofadditives. Suitable additives include, without limitation, antioxidants,catalysts, lubricants, low molecular weight non-crosslinking resins,adhesion promoters, and stabilizers. Some additives can operate tocontrol the polymerization process, thereby affecting the physicalproperties (e.g., modulus, glass transition temperature) of thepolymerization product formed from the composition. Others can affectthe integrity of the polymerization product of the composition (e.g.,protect against de-polymerization or oxidative degradation).

A non-exhaustive list of optional preferred additives includessurfactants, surface agents, slip additives, waxes,micronized-polytetrafluoroethylene, and combinations thereof. Preferablya surfactant comprises a compound which includes one or more polarsections and one or more non-polar sections. A surfactant is not limitedto only a compound which modifies surface conditions. Preferably asurface agent is a particular type of surfactant which may be used tomodify surface conditions.

Other suitable materials for use in secondary coating materials, as wellas considerations related to selection of these materials, are wellknown in the art and are described in U.S. Pat. Nos. 4,962,992 and5,104,433 to Chapin, each of which is hereby incorporated by referencein its entirety.

Optical fibers useful in preparing optical fiber ribbons of the presentinvention can be of any conventional design and construction, such asthe type described above. The primary and secondary coating compositionsare coated on a glass fiber using conventional processes, for example,on a draw tower. It is well known to draw glass fibers from a speciallyprepared, cylindrical preform which has been locally and symmetricallyheated to a temperature, e.g., of about 2000° C. As the preform isheated, such as by feeding the preform into and through a furnace, aglass fiber is drawn from the molten material. One or more coatingcompositions are applied to the glass fiber after it has been drawn fromthe preform, preferably immediately after cooling. The coatingcompositions are then cured to produce the coated optical fiber. Themethod of curing can be thermal, chemical, or radiation induced, such asby exposing the applied (and un-cured) coating composition on the glassfiber to ultraviolet light, actinic radiation, microwave radiation, orelectron beam, depending upon the nature of the coating composition(s)and polymerization initiator being employed. It is frequentlyadvantageous to apply both primary and secondary coating compositions insequence following the draw process. One method of applying dual layersof coating compositions to a moving glass fiber is disclosed in U.S.Pat. No. 4,474,830 to Taylor, which is hereby incorporated by referencein its entirety. Another method for applying dual layers of coatingcompositions onto a glass fiber is disclosed in U.S. Pat. No. 4,851,165to Rannell et al., which is hereby incorporated by reference in itsentirety. Of course, the primary coating composition can be applied andcured to form the primary coating material, then the curable compositiondescribed hereinabove can be applied and cured to form the curedpolymeric material of the secondary coating.

The curable secondary coating compositions may also be advantageouslyused in the formulation of marking inks for optical fibers. As notedabove in reference to FIG. 2, the coated optical fiber 20 can alsoinclude a marking ink 28 deposited on the exterior of the coatingsystem, e.g., the dual coating system as described above. A marking inkis typically formed as a thin layer of a colored coating on the outersurface of a secondary coating of an optical fiber. The marking ink canbe formed by adding pigments and/or dyes to a pigment binder phase(i.e., a curable secondary coating composition containing oligomer(s)and monomer(s) and co-monomers). The co-monomer components arepreferably polar, non acrylate monomers (e.g., N-vinyl caprolactammonomer).

Preferred marking inks include a pigment binder phase, a pigment or dye,and a phosphine oxide photoinitiator, wherein the ink formulation ischaracterized by a cure speed of at least about 80 percent acrylateconversion/second, more preferably between about 80 and about 500percent acrylate conversion/second, or between about 100 and about 400percent acrylate conversion/second. Desirably, the ink formulation ischaracterized by either a T_(g) value that is at least about 60° C., aK_(1C) value that is at least about 0.8 MPa·m^(1/2), or both. Cure speedis a measure of the percent of acrylate conversion per second(percent/s). The percentage of cure was evaluated in accordance with theFourier Transform Infrared Spectroscopy analyses. Basically, an uncuredfilm is applied to an ASI DuraSamplir® ATR crystal (or equivalent) at ˜1mm thickness, the film is purged with nitrogen for 30 sec, and thenirradiated to induce polymerization with, e.g., Lesco Mark II Spot cureunit and UniBlitz® VS25 Shutter Assembly with model T132 driver. Theshutter is opened for a 1 sec exposure, and spectra are collected at 6ms intervals for 0.9 sec. Following the 0.1 sec pause, spectra are againcollected for 5 sec following initial exposure. The shutter again opensfor a 10 sec exposure, which allows for calculation of the 100% cureband ratio. Both uncured and fully cured band ratio are calculated foreach, and a cure vs. time plot is constructed using conventionalsoftware, e.g., OPUS v3.04 in OS/2 (Spectrometer operation and datamanipulation), Galactic Grams32 v5.02, and MicroCal Origin v6.0. Thepolymerization rate, Rp, can be calculated at any point in the curvefrom the slope of the curve, and the maximum polymerization rate ispreferably estimated as the slope of the curve from 10% conversion to40% conversion. The reported cure speed number is the slope of the linewithin this range

Preferred pigments or dyes are preferably not greater than about 1micron. Exemplary pigments and dyes (and the respective colors thereof)include, without limitation: titanium dioxide, which is a white pigment;phthalocyanine blue and indanthrone blue, which are blue pigments; azoyellow, diarylide yellow, and isoindolinone yellow, which are yellowpigments; phthalocyanine green, which is a green pigment; azo red,naphthol red, and perylene red, which are red pigments; carbon blacks,which are black pigments; pyrazolone orange, which is an orange pigment;and _carbazole and quinacridone violet, which are violet pigments; Theremaining colors of brown, slate, aqua and rose can be made using theappropriate combinations of the above listed pigments. Other pigmentsare known and others are continually being developed so that they havecure speeds within the above-noted ranges and preferences in thepreceding paragraphs.

Preferred cure speeds are accomplished by formulating inks that containeither a MAPO or BAPO photoinitiator blend in conjunction with Irgacure184, an optical brightener, and a small amount of N-vinyl caprolactammonomer. Another aspect of the formulation that contributes to thepreferred cure speeds is the optimization of the pigment dispersion suchthat substantially all pigment particles (i.e., 99 percent or more) areless than about 1 micron in size. This very small average particle sizeresults in higher tint strengths, which allows lower pigment levels tomeet the desired color targets.

Additional components that can be added to facilitate the desired curedproperties include coupling agents (e.g., titanates or zirconates asdescribed in U.S. Pat. No. 6,553,169 to Fabian, which is incorporatedherein by reference in its entirety), surface action agents (e.g., slipagents such as TegoRad 2250, a silicone polyether acrylate availablefrom Tego Chemie/Goldschmidt Chemical Corp.; anti-static agents andmatting agents, and combinations thereof.

The ribbons 10 of the present invention can be fabricated usingpreviously formed optical fibers 20 prepared as described above. Thematrix 30 is the cured product of a curable composition, preferably acomposition that is, itself, suitable for use as a secondary coating onan optical fiber. The matrix can be formed of a curable composition thatis the same as the secondary coating on the plurality of optical fibers,or the matrix can be formed of a different curable composition.

One embodiment of a ribbon of the present invention is illustrated inFIG. 1. As shown therein, fiber optic ribbon 10 of the present inventionincludes a plurality of single or multi-layered optical fibers 20substantially aligned relative to one another in a substantially planarrelationship and encapsulated by matrix 30. The skilled artisan willappreciate that the optical fibers 20 may include a dual-layer coatingsystem (for example, the primary and secondary coatings describedhereinabove), and may be colored with a marking ink. It is desirablethat optical fibers 20 are not displaced from a common plane by adistance of more than about one-half the diameter thereof. Bysubstantially aligned, it is intended that the optical fibers 20 aregenerally parallel with other optical fibers along the length of thefiber optic ribbon 10. In FIG. 1, the fiber optic ribbon 10 containssixteen (16) optical fibers 20; however, it should be apparent to thoseskilled in the art that any number of optical fibers 20 (e.g., two ormore) may be employed to form fiber optic ribbon 10 disposed for aparticular use.

The optical fibers in fiber optic ribbons of the present invention maybe encapsulated by the matrix 30 in any known configuration (e.g.,edge-bonded ribbon, thin-encapsulated ribbon, thick-encapsulated ribbon,or multi-layer ribbon) by conventional methods of making fiber opticribbons.

The fiber optic ribbon may be prepared by conventional methods usingappropriate curable compositions to form the matrix material. Forexample, upon alignment of a plurality of substantially planar opticalfibers, the desired ink and matrix compositions can be applied and curedaccording to the methods of preparing optical fiber ribbons as describedin U.S. Pat. No. 4,752,112 to Mayr and U.S. Pat. No. 5,486,378 toOestreich et al., each of which is incorporated herein by reference inits entirety. Curing of the ink layer and matrix layer(s) can beperformed as a single step or as multiple steps following eachapplication.

To facilitate improved ribbon stripability in accordance with thepresent invention, the optical fiber coating (e.g., secondary coating),the optional ink layer, and the matrix material are characterized bymatched or compatible thermal-mechanical properties.

According to one approach, the two or more of the various polymericmaterials that are adjacent to one another (i.e., the fiber coating(s),the optional ink layer, and the matrix material(s)) are formed from asimilar base composition. That is, the base formulation for thepolymeric material is either identical (containing exactly the sameamount of the same monomer and oligomer components prior to the additionof any additives specific for the particular application) orsubstantially the same. That is, the base formulation can contain aminor variation, e.g., less than about 10 percent or more preferablyless than about 5 percent variation in the amount of monomer or oligomercomponents, replacement of one or more monomer or oligomer componentswith an analog equivalent thereof, or both.

As used herein, the term “matched or compatible thermal-mechanicalproperties” is intended to reflect that two or more of the variouspolymeric materials that are adjacent to one another possess one or moreclosely related thermal-mechanical properties. That is, thethermal-mechanical property of interest indicates that the two materialswill behave similarly under applied thermal or stress conditions.Exemplary thermal-mechanical properties include, without limitation,glass transition temperature (T_(g)), fracture toughness (K_(1C)),tensile (Young's) modulus, and ductility.

One aspect of the present invention relates to an optical fiber ribbonthat includes a plurality of optical fibers encapsulated within a matrixmaterial, where the optical fiber coating(s) and the matrix material(s),and optionally any ink layers thereon, are characterized by compatiblechemical and/or thermal-mechanical properties, whereby the coatings andmatrix and any ink layers therebetween can be reliably stripped from theoptical fibers to afford a suitable strip cleanliness.

According to one embodiment, the coating, matrix, and ink layer (ifpresent) are each characterized by a T_(g) value, a K_(1C) value, atensile modulus value, and a ductility parameter value, and one or moreof the following conditions are satisfied:

-   -   (i) the difference between the highest and lowest of the        respective T_(g) values is less than about 15° C., preferably        less than about 14°, 13°, 12°, 11°, or 10° C., more preferably        less than about 9°, 8°, 7°, 6°, or 5°, most preferably less than        about 4°, 3°, 2°, or 10° C.;    -   (ii) each of the T_(g) values is greater than about 60° C.;    -   (iii) the respective K_(1C) values are at least about 0.8        MPa·m^(1/2), preferably at least about 0.85, 0.90, 0.95, or 1.0,        more preferably at least about 1.05, 1.1, 1.15, or 1.2        MPa·m^(1/2), most preferably at least about 1.25, 1.3, 1.35, or        1.4 MPa·m^(1/2);    -   (iv) the difference between the highest and lowest of the        respective tensile modulus values is less than about 500 MPa,        more preferably less than about 450, 400, 350, or 300 MPa, most        preferably less than about 250, 200, 150, or 100 MPa;    -   (v) the ductility value is at least about 350 microns, more        preferably at least about 360, 370, 380, 390, or 400 microns,        most preferably at least about 410, 420, 430, 440, or 450        microns; or    -   (vi) any combination of two or more of (i)-(v), more preferably        three or more of (i)-(v), and most preferably four or five of        (i)-(v).        Thus, in the absence of an ink layer, the differences between        the T_(g) values and/or tensile modulus values of the optical        fiber (secondary) coating and the (inner) matrix are directly        compared. In the presence of the ink layer, however, only the        highest and lowest values of the three are compared.

The glass transition temperature (T_(g)) refers to the temperature belowwhich a coating (or ink or matrix) material is brittle and above whichit is flexible. An alternative (and more accurate) definition is basedon the fact that at the glass transition temperature, the coefficient ofthermal expansion changes sharply. The glass transition temperature canbe a single degree or a short range of degrees. It is preferable thatthe glass transition temperature for one or more (more preferably two ormore, and most preferably all three) of the coating, the ink, and matrixis greater than 60° C.

The glass transition temperature (T_(g)) of polymeric materials may bemeasured by a variety of techniques such as differential scanningcalorimetry (DSC) or dynamic mechanical analysis (DMA). The coatingsevaluated in this body of work were done so by the use of the DMA. InDMA analysis (and in the data presented in this application) the valueused for the T_(g) is frequently defined as the maximum of the tan δpeak, where the tan δ peak is defined as:tan δ=E″/E′where E″ is the loss modulus, which is proportional to the loss ofenergy as heat in a cycle of deformation and E′ is the storage orelastic modulus, which is proportional to the energy stored in a cycleof deformation. See Ferry, J. D. In Viscoelastic Properties of Polymers,3^(rd) ed., Wiley: New York, 1980, Chapter 1. The maximum value of thetan delta peak, while serving as a convenient measure of the Tg,typically exceeds the value that is obtained when the Tg is measured bymethods such as DSC.

The T_(g) value as measured for cross linked materials, also willtypically give rise to broader peaks than will be obtained innon-crosslinked polymeric materials. For materials that are crosslinked,the ranges of T_(g) overlap described earlier are appropriate for use inthis invention, but the overlap for lower crosslink density ornon-crosslinked thermoplastic materials may be more complete.

The resistance of a material to unstable, catastrophic crack growth isdescribed by the material property known as fracture toughness, K_(1C).The fracture toughness of a material relates to the energy required topropagate a crack in the material. As used herein, fracture toughnessK_(1C) is measured on film samples, and is defined as Yσ√{square rootover (z)}, where Y is a geometry factor, σ is the tensile strength (atbreak) of the film sample, and z is half of the notch length. Fracturetoughness is measured on films having a center cut notch geometry. FIG.3 is a schematic depiction of the sample geometry used in measuringfracture toughness. Film sample 80 has a width of about 52 mm, and isabout 0.010″ (254 μm) in thickness. A notch 82 is cut in the center ofthe film using a sharp blade using methods familiar to the skilledartisan. Notches having lengths of 18 mm, 24 mm, and 30 mm are cut indifferent samples. The tensile strength (at failure) of the sample, σ,is measured using a tensile testing instrument (e.g. a Sintech MTSTensile Tester, or an Instron Universal Material Test System), asdescribed above. The sample is gripped in the jaws 84 of the tensiletesting instrument such that the gauge length is 75 mm. The displacementrate is 2.0 mm/min. The tensile strength may be calculated by dividingthe applied load at failure by the cross-sectional area of the intactsample. For the samples described above, the tensile strength may becalculated using the equation

$\sigma = {\frac{Load}{254\mspace{14mu}\mu\; m\mspace{14mu}\left( {{52\mspace{14mu}{mm}} - {2z}} \right)}.}$Y is a geometry factor, and is defined as 1.77−0.177(2λ)+1.77(2λ)²,where λ=z/sample width.

The tensile (Young's) modulus value is a measure of the stress appliedto a sample (of the coating material, ink layer, or matrix material) atthe time of breakage. It is preferable that the tensile modulus for oneor more (more preferably two or more, and most preferably all three) ofthe coating, the ink, and matrix is at least about 1200 MPa, morepreferably at least about 1500 MPa, most preferably at least about 1900MPa. As used herein, the Young's modulus, is measured using a tensiletesting instrument (e.g. a Sintech MTS Tensile Tester, or an InstronUniversal Material Test System) on a sample of a material shaped as acylindrical rod about 0.0225″ (571.5 μm) in diameter, with a gaugelength of 5.1 cm, and a test speed of 2.5 cm/min.

The sensitivity of the cured polymeric material of the secondary coating(or matrix or ink layer) to handling and the formation of defects isreflected by its ductility. The ductility of a material is defined bythe equation

${Ductility} = {\left( \frac{K_{1C}}{{yield}\mspace{14mu}{stress}} \right)^{2}.}$Larger ductilities indicate reduced sensitivity of the secondary coatingto handling and defect formation. Yield stress can be measured on therod samples at the same time as the Young's modulus, elongation tobreak, and tensile strength, as described above. As is familiar to theskilled artisan, for samples that exhibit strain softening, the yieldstress is determined by the first local maximum in the stress vs. straincurve. More generally, the yield stress can be determined using themethod given in ASTM D638-02, which is incorporated herein by referencein its entirety.

According to another embodiment, the coating, matrix, and ink layer (ifpresent) are each formed of a similar curable base formulation. That is,prior to forming the coating, matrix, or ink layer, the base formulationof oligomers and monomers is substantially similar and, consequently,compatible for use together.

A preferred base composition that can be used for the secondary coating,the marking ink, and/or the matrix includes: 20 weight percent ofPhotomer 3016, a high viscosity epoxy acrylate monomer (Cognis); 77weight percent of Photomer 4028, an ethoxylated (4 moles) bisphenol Adiacrylate monomer (Cognis); 1.5 weight percent Lucirin TPO, a2,4,6-trimethylbenzoyl-diphenyl phosphine oxide (BASF); 1.5 weightpercent Irgacure 184, a hydroxy-cyclohexyl phenyl ketone (Ciba)); and0.5 pph Irganox 1035, a thiodiethylene bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate} (Ciba).

Having prepared an optical fiber ribbon of the present invention, theribbon is intended to be integrated into an optical fiber datatransmission system, such as the type used in telecommunication systems.

EXAMPLES

The following examples are provided to illustrate embodiments of thepresent invention but are by no means intended to limit its scope.

Example 1 Preparation of Optical Fiber Ribbons

Optical fiber ribbons were fabricated using previously prepared opticalfibers that possessed either a high T_(g) (>60 C) secondary coating(“Coating A”) or a lower T_(g) (<55 C) secondary coating (“Coating B”).

Ink compositions that were used to cover the optical fibers includedeither DSM-LTS (“Ink A”), an ink coating commercially available from DSMDesotech, Inc. (Elgin, Ill.); a base composition containing 20% Photomer3016 (Cognis), 77% Photomer 4028 (Cognis), 1.5% Lucirin TPO (BASF), 1.5%Irgacure 184, and 0.5 pph Irganox 1035 (“Ink B”) or a base compositioncontaining 10% KWS4131 (Bomar), 5% Photomer 3016 (Cognis), 82% Photomer4028 (Cognis), 1.5% Lucirin TPO (BASF), 1.5% Irgacure 184 (Ciba) and 0.5pph Irganox 1035 (Ciba) (“Ink C”)

Dual matrix systems included both an inner matrix and an outer matrix.Inner matrix materials included either DSM 950-716, a urethane acrylatebased matrix material commercially available from DSM Desotech, Inc.(“Inner Matrix A”), the base composition of Ink B absent any pigments(“Inner Matrix B”), or the base composition of Ink C absent any pigments(“Inner Matrix C”). The outer matrix material that was used was DSM9D9-518 from DSM Desotech, Inc.

All ribbons were prepared using a dual-layer, 12-fiber dry lock systemusing standard manufacturing procedures. A total of four ribbons wereprepared as described in Table 1 below. The physical properties of thevarious coatings, inks, and inner and outer matrices are provided inTable 2 below.

TABLE 1 Construction of Dual Layer Matrix Ribbons Secondary Ribbon No.Fiber Coating Ink Inner Matrix Outer Matrix 1 Coating A Ink A InnerMatrix A Outer Matrix A 2 Coating A Ink A Inner Matrix B Outer Matrix A3 Coating A Ink B Inner Matrix B Outer Matrix A 4 Coating B Ink C InnerMatrix C Outer Matrix A

TABLE 2 Physical Properties of Fiber Coatings, Inks, and MatrixMaterials Tensile T_(g) Value K_(1C) Value Modulus Ductility PolymerMaterial (° C.) (MPa · m^(1/2)) (MPa) (in microns) Secondary Fiber 801.2655 1900 403 Coating A Secondary Fiber 55 0.7587 1500 390 Coating BInk A 75 0.6955 1505 274 Ink B 80 1.2655 1900 403 Ink C 55 0.7587 1500390 Inner Matrix A 57 0.6809 1100 229 Inner Matrix B 80 1.2655 1900 403Inner Matrix C 55 0.7587 1500 390

Example 2 Testing of Ribbons for Strip Cleanliness

All ribbons were stripped using a Sumitomo JR4A stripper set at 90° C.,the purpose of which was to simulate worst case conditions that may befound in the field. Stripping was performed by hand, at eithersubjectively defined slow or fast rates. Ribbon strip performance wasevaluated with ratings assigned for both cleanliness and tube-off.

Strip cleanliness was measured by examining the stripped optical fiberfor debris. As described above, a score of one (1) identifies a fiberhaving a low amount of debris on its surface and a score of five (5)represents a fiber having a significant amount of debris on its surface.Any score of three (3) or less was deemed to be acceptable stripcleanliness. Cleanliness measurements were obtained by visuallyinspecting a segment of the stripped ribbon fibers with the naked eye.Particles remaining on the stripped ribbon fibers were examined andcompared to limit samples which were rated according to the followingstandard:

Number of Particles Cleanliness Rating  0-10 1 11-20 2 21-40 3 >40 andneeds extra cleaning 4 >40 and extra cleaning ineffective 5A total of five segments were measured for each ribbon, and the averagescore appears in Table 3 below.

Tubeoff values were measured by examining the integrity of the tube andcomparing it to limit samples in order to assign a value of 1 to 5 witha score of one (1) meaning that the tube is totally intact in one unitand a score of five (5) meaning that the tube totally disintegrated inthe strip tool.

TABLE 3 Strip Cleanliness of Stripped Ribbons Fast Strip Fast Strip SlowStrip Slow Strip Ribbon No. Cleanliness Tubeoff Cleanliness Tubeoff 12.0 4.0 2.4 2.2 2 2.0 4.0 2.0 1.6 3 2.0 2.0 1.0 1.0 4 2.0 4.4 2.0 4.6The best results were obtained from Ribbon 3, which possessed asecondary fiber coating, ink layer, and inner matrix that were formedfrom the same base formulation. The good tubeoff performance can beattributed to the high T_(g) of this shared base formulation (80° C.),which helps to maintain the integrity of the tube at the striptemperature, and the good adhesion between the layers, which preventsdelaminations in the tube during strip operations. Ribbon 4 demonstratesthe preference of using polymeric materials having T_(g) values ofgreater than about 60° C. Ink C and inner matrix C are characterized bya T_(g) in the range of about 50-55 C.

Example 3 Comparison of Marking Ink Degree of Cure

Ink formulations were prepared using one or more of the followingcomponents: Photomer 3016, a high viscosity epoxy acrylate monomer(Cognis); Photomer 4028, an ethoxylated (4 moles) BPA diacrylate monomer(Cognis); V-Cap/RC, n-vinyl caprolactam monomer from ISP Corporation;Lucirin TPO, 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide (BASF);Irgacure 184, a hydroxy-cyclohexyl phenyl ketone (Ciba); Uvitex OB, a2,5-thiophenediylbis(5-tert-butyl-1,3-benzoxazole) optical brightener(Ciba); Irganox 1035, a thiodiethylene bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate} (Ciba); and TegoRad2250, a silicone polyether acrylate slip agent (Tego Chemie/GoldschmidtChemical Corp., Hopewell, Va.).

The above base formulation was combined with the appropriate pigments toprepare violet, red, white, blue, brown, and black inks.

In addition, Cablelite 751 ink formulations obtained from DSM Desotechwere compared side-by-side to the above inks.

The various ink formulations were coated onto optical fibers and passedthrough a die to control thickness to 3-5 μm. Fibers were cured at aline speed of 1000 m/min with 100% lamp power using a D bulb. The degreeof cure for each marking ink was determined by depletion of acrylategroups as determined via Fourier Transform InfraRed Spectroscopy usingstandard attenuated total internal reflection methods typically used incoatings industry. The results of the degree of cure measurements arepresented in Table 4 below.

Color DSM Ink Inventive Ink Violet 77.07 91.42 Red 73.83 92.79 White78.62 90.10 Blue 73.62 95.06 Brown 68.79 93.08 Black 81.46 94.65

The above data demonstrates that the ink formulations of the presentinvention can achieve significantly higher degrees of cure (undersimilar UV doses) than one of the more preferred commercially availableink formulations. This will allow even higher processing speeds duringink coating and ribbon formation, as well as minimize defects duringmanufacture.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the spirit and scope of the invention. Thus, itis intended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. An ink formulation comprising a pigment binder phase comprising oneor more oligomer and/or monomer components having an acrylate functionalgroup, a polar non-acrylate monomer component, a pigment or dye, anoptical brightener, and a phosphine oxide photoinitiator, wherein theink formulation is characterized by a cure speed of at least about 80percent acrylate conversion/second for the colors blue, green, yellow,black and brown; about 110 percent acrylate conversion/second for thecolor red; about 130 percent acrylate conversion/second for the colorsorange and aqua; about 140 percent acrylate conversion/second for thecolors white, violet and rose; and about 150 percent acrylateconversion/second for the color slate.
 2. The ink formulation accordingto claim 1, wherein the ink formulation has a cure speed of betweenabout 80 and about 500 percent acrylate conversion/second.
 3. The inkformulation according to claim 1, wherein the polar non-acrylate monomercomponent is an N-vinyl caprolactam.
 4. The ink formulation according toclaim 1, wherein the ink formulation comprises pigment that is notgreater than about 1 micron.
 5. The ink formulation according to claim1, wherein the optical brightener is2,5-thiophenediylbis(5-tert-butyl-1,3-benzoxazole).
 6. The inkformulation according to claim 1 further comprising a surface activeagent.
 7. The ink formulation according to claim 6, wherein the surfaceactive agent is selected from the group consisting of slip agents,anti-static agents, and matting agents.
 8. The ink formulation accordingto claim 1, wherein a cured product of the ink formulation has either aT_(g) value that is at least about 60° C., a K_(1C—)value that is atleast about 0.8 MPa·m^(1/2), or both.
 9. The ink formulation accordingto claim 1, wherein a cured product of the ink formulation has a K_(1C)value that is at least about 0.8 MPa·m^(1/2).
 10. The ink formulationaccording to claim 1, wherein a cured product of the ink formulation hasa K_(1C) value that is at least about 1.0 MPa·m^(1/2).
 11. The inkformulation according to claim 1, wherein a cured product of the inkformulation has a K_(1C) value that is at least about 1.2 MPa·m^(1/2).12. The ink formulation according to claim 1, wherein a cured product ofthe ink formulation has a ductility value that is at least about 350microns.
 13. The ink formulation according to claim 1, wherein a curedproduct of the ink formulation has a ductility value that is at leastabout 400 microns.
 14. The ink formulation according to claim 1, whereinthe ink formulation achieves a degree of cure in excess of 90% whenapplied to a fiber at a thickness of 3-5 μm and exposed to a D bulb atfull power and a line speed of 1000 m/min.